People protest the Keystone XL Pipeline project in front of the White House in Washington on Sept. 2, 2011. / File photo by Luis Alvarez, AP

by Wendy Koch, USA TODAY

by Wendy Koch, USA TODAY

A slight majority of Americans favor the controversial Keystone XL oil pipeline that President Obama is expected to approve or reject this year, finds a poll conducted for USA TODAY.

About 56% say they favor the northern leg of the billion-dollar, Canada-to-U.S. project and 41% oppose it, according to the poll of 801 U.S. adults completed last month by Stanford University and Resources for the Future (RFF), a non-partisan research group.

More men (60%) than women (53%) support the 1,179-mile pipeline extension, which would carry heavy tar sands from Alberta through Montana and South Dakota to Steele City, Neb. Support was consistent regardless of education level but much stronger among self-described conservatives than liberals, a slight majority of whom oppose it.

"These findings are suggestive but not conclusive," says Phil Sharp, president of RFF, which funded the Nov. 20-Dec. 5. poll. "We simply don't know how firm people's attitudes are about this."

The pipeline, proposed by Calgary-based TransCanada, has become one of the most contentious issues of Obama's presidency. Environmentalists have waged a grass-roots war against it, saying tar sands' development would worsen global warming and its delivery could risk oil spills. The oil industry and other backers say it would increase jobs and reduce U.S. dependence on unreliable foreign sources of oil.

"It has tremendous symbolic value to a lot of people," says Sharp, a former Democratic member of Congress, noting how critics see the pipeline as a litmus test of Obama's commitment to fighting climate change and backers view it as a test of his support for economic growth.

So far, Obama hasn't shown his hand, at least not publicly. In June, while unveiling his plan to cut U.S. carbon emissions, he said he could only back the pipeline if it does not "significantly exacerbate the problem of carbon pollution." Both sides see his opaque comment as bolstering their arguments.

The project has dangled in Washington for years, mired in lengthy environmental impact studies. The State Department is overseeing the review, because the pipeline crosses an international border. Its draft last March irked environmentalists by saying Keystone won't matter much, because Canada's tar sands will likely be extracted with or without it.

Secretary of State John Kerry told reporters earlier this month that the final review would be out "before long." That review will trigger a 90-day federal process for determining if the project is in the nation's interest. The ultimate decision isn't expected until late spring at the earliest.

All 45 Senate Republicans urged Obama earlier this month to end the delays. "We are well into 2014 and you still have not made a decision," they said in a letter. House Republicans have repeatedly tried to tie Keystone's approval to key pieces of legislation.

On Tuesday, before Obama's State of the Union address, Keystone critics paraded a 100-yard inflatable pipeline around the Capitol, emblazoned with the words "Climate Champion or Pipeline President." Billionaire activist Tom Steyer planned a minute-long, anti-pipeline TV ad to air before and after Obama's speech.

In January 2012, Obama rejected the initial 1,700-mile version from Alberta to Port Arthur, Texas, saying he needed more time for environmental review. So TransCanada split the project into two and revised the route of the northern leg to avoid environmentally sensitive areas in Nebraska. The 485-mile southern leg, from Cushing, Okla., to the Gulf Coast, became operational last week.

"It's terribly complicated, because you know there are jobs at stake but also environmental issues," says Richard Kedward, a Seattle resident queried in the USA TODAY poll. "Being an independent person, it's very conflicting."

Julianna Puskas of Techachapi, Calif., says the pipeline "would be good for us." She adds: "I'd rather support Canada selling us oil than other countries."

"The more Americans learn about the pipeline, the less they like it," says Danielle Droitsch of the Natural Resources Defense Council, an environmental group. She says tar sands oil is more corrosive and its extraction emits more greenhouse gases than conventional crude oil. She says the USA TODAY poll shows support for Keystone is eroding while opposition is growing.

Polls earlier last year by Pew Research Center found consistently higher support -- two-thirds in favor -- of the pipeline, but they found opposition rising from 23% in March to 30% in September. A Bloomberg National Poll, taken Dec. 6-9, found 56% in favor and 35% opposed.

Findings can vary because of differences, however slight, in how a question is phrased. The USA TODAY poll, conducted by Abt SRBI, has a margin of error of plus or minus 4.2 percentage points.